Vantah v0.3.2

Domains tab no longer looks empty while it loads

Until adguardvpn-cli site-exclusions show answered, the tab showed an empty list with working
buttons — which reads as "there are no exclusions", even though they had not been fetched yet.
The tab now has the same three states as Locations and Settings:

• Loading — skeleton placeholders matching the layout of the screen, in place of both the list
  and the buttons, so nothing can be clicked before the real list is known.
• Failed load — the error text and a Refresh button in the middle of the tab, instead of
  silent emptiness.
• Loaded — the list itself.

The skeleton only appears while there is no data yet: the list is reloaded after every
add/remove/import, and an already visible list is never collapsed back into placeholders.

Other changes

• Tray menu: Show window moved to the top, right after the status line — it used to sit
  below the location entries, although reopening the window is the most common reason to use the menu.
• About window is now sized to its content (460×280) instead of the default 560×720, which left
  half the window empty.